The present invention relates to an optical disk drive having optics which includes an objective lens for recording and reproducing optical data out of an optical disk and, more particularly, to an optics support for an optical disk drive which allows an objective optical lens to move in a focusing and a tracking direction relative to the recording surface of a disk.
Today, a video disk drive, digital audio disk drive, optical filing system or similar optical disk drive is extensively used for recording and reproducing optical data out of an optical information recording medium, or disk. Specifically, pits representative of data are formed in an optical disk in a spiral track configuration. To playback the disk, while the disk is rotated at a predetermined speed, the track on the disk is illuminated by a spot beam so that a variation in the intensity of the resulting reflected or transmitted light is converted into an electric signal representative of the original data. A prerequisite with the playback is that the spot beam be accurately focused onto the recording surface of a disk. Therefore, the optics have to be supported such that an objective lens therefore is movable in a focusing direction which is perpendicular to the recording surface of a disk, i.e., along the axis of the objective lens. The optics also have to be supported in such a manner as to allow the objective lens to move along the radius of a disk, i.e., in a tracking direction, so that the spot beam may accurately track the disk at all times. To meet these requirements, optics with an objective lens are generally supported by a device which is made up of a support mechanism for supporting the optics while allowing it to move in the focusing and tracking directions, and a drive mechanism for driving the optics in the two different directions in response to a focusing error signal and a tracking error signal. This type of optics support arrangement is disclosed in Japanese Patent Laid-Open Publication (Kokai) Nos. 59-104733 and 61-48142 and U.S. Pat. No. 4,759,005 (Kasahara), for example.
The support mechanism mentioned above has customarily been implemented by a pair of thin leaf springs each being deformable in a different direction, i.e., in the focusing or the tracking direction. These leaf springs, or resilient members, support the objective lens of the optics such that the lens is movable. The drive mechanism associated with the support mechanism has a first and a second drive coil for displacing the lens in the focusing direction and the tracking direction, respectively. When currents individually associated with the focusing error and tracking error signals are applied to the independent drive coils, the leaf springs are deformed to displace the lens in their predetermined directions. The position of the lens is finely adjusted in this way by the deformation of the leaf springs in the focusing and tracking directions as effected by the drive mechanism.
A problem with the above described type of drive mechanism is that the leaf springs are apt to undergo resonance during operation. For example, assume that the objective lens is displaced in the tracking direction. Then, the lens is displaced in the focusing direction also, so that a twisting force and, therefore, resonance occur due to the deviation between the point where the resulting force acts and the point where the leaf spring exerts a reaction. To eliminate the resonance and thereby enhance the damping characteristic, each of the leaf springs has heretofore been provided with a laminate structure made up of a sheet-like resilient member, and vibration-preventing or -suppressing members provided on opposite sides of the resilient member and made of butyl rubber or silicon rubber, for example. However, a satisfactory vibration-suppressing effect is not achievable with the leaf springs unless their vibration-suppressing members have adequate hardness and are about 0.05 millimeters to 0.3 millimeters thick. This, coupled with the fact that such vibration-suppressing members have to be adhered or otherwise connected to opposite sides of the elastic member, renders the production line complicated. With an adhesive, for example, it is not easy to accomplish a desired vibration-suppressing effect because applying it uniformly is difficult. Further, the assembly of the leaf springs of the support mechanism involves a substantial degree of scattering, also aggravating the damping characteristic.